diff --git a/docs/00-series-overview.md b/docs/00-series-overview.md new file mode 100644 index 0000000..0b26080 --- /dev/null +++ b/docs/00-series-overview.md @@ -0,0 +1,262 @@ +# OTA Reference Design + +> A practical guide to designing reliable, secure, and maintainable over-the-air (OTA) update systems for embedded Linux devices. + +--- + +## About This Repository + +This repository presents a practical reference design for building over-the-air (OTA) update systems for embedded Linux devices. + +Rather than documenting a particular framework or vendor-specific solution, it focuses on the engineering principles that make OTA systems reliable, secure, and maintainable. + +The goal is to explain **why** modern OTA systems are designed the way they are, what problems they solve, and what trade-offs different approaches involve. + +Although many examples use Raspberry Pi as a demonstration platform, the concepts are applicable to a wide range of embedded Linux systems. + +--- + +## Why This Repository Exists + +There is no shortage of documentation for OTA frameworks. + +You can easily find documentation for tools such as: + +- Mender +- RAUC +- SWUpdate +- OSTree +- A/B Updates + +However, these resources usually explain **how to use a particular tool**, not **why OTA systems are designed this way**. + +Questions like these are often left unanswered: + +- Why do many devices use A/B partitions? +- Why are bootloaders involved in the update process? +- Why is rollback necessary? +- What happens if power is lost during an update? +- Why are update images signed? +- Why are atomic updates important? +- How do production devices remain recoverable after failures? + +This repository attempts to answer those engineering questions. + +--- + +## What You'll Learn + +Throughout this series we will explore topics including: + +- OTA architecture +- Boot process +- Update strategies +- Full-image vs package updates +- A/B partition layouts +- Bootloader interaction +- Rollback mechanisms +- Atomic updates +- Image verification +- Digital signatures +- Secure Boot +- Failure recovery +- Delta updates +- Version management +- Testing strategies +- Production deployment considerations + +The emphasis is always on understanding the underlying design rather than memorizing a particular implementation. + +--- + +## Repository Structure + +```text +ota-reference-design/ +│ +├── docs/ +│ ├── 00-series-overview.md +│ ├── 01-ota-introduction.md +│ ├── 02-update-strategies.md +│ ├── ... +│ +├── diagrams/ +│ └── plantuml/ +│ +├── examples/ +│ ├── raspberry-pi/ +│ ├── qemu/ +│ └── simulations/ +│ +├── adr/ +│ ├── ADR-001-repository-name.md +│ ├── ADR-002-license.md +│ └── ADR-003-reference-design.md +│ +└── README.md +``` + +--- + +## Learning Path + +The chapters are designed to build on each other. + +```text +Introduction + │ + ▼ +Update Strategies + │ + ▼ +System Architecture + │ + ▼ +Boot Process + │ + ▼ +Storage Layout + │ + ▼ +Atomic Updates + │ + ▼ +Rollback + │ + ▼ +Security + │ + ▼ +Testing + │ + ▼ +Production Deployment +``` + +While each chapter can be read independently, following the series in order provides a much deeper understanding of the complete system. + +--- + +## Engineering Philosophy + +This repository is intentionally different from product documentation. + +Instead of presenting a single "correct" solution, every topic discusses: + +- why a particular design exists; +- which problem it solves; +- what alternatives are available; +- what trade-offs each approach introduces; +- when another solution may be more appropriate. + +Real-world engineering is rarely about choosing the only correct answer. + +It is about understanding constraints and making informed decisions. + +--- + +## The Reference Design + +The architecture presented throughout this repository is a coherent reference design. + +Real products may use different technologies or frameworks while following the same architectural principles. + +For example, one project may use RAUC, another SWUpdate, and another a completely custom implementation. + +The implementation details may differ. + +The underlying engineering principles usually do not. + +--- + +## Practical Examples + +Where possible, theoretical discussions are accompanied by practical material, including: + +- architecture diagrams +- boot sequence walkthroughs +- storage layout examples +- failure scenarios +- Raspberry Pi demonstrations +- QEMU-based experiments +- implementation notes + +The objective is to connect high-level architecture with practical implementation. + +--- + +## Intended Audience + +This repository is intended for: + +- Embedded Linux developers +- Firmware engineers +- Embedded software engineers +- System architects +- Students learning embedded systems +- Engineers preparing for technical interviews +- Anyone interested in understanding OTA system design + +No prior experience with OTA frameworks is assumed. + +--- + +## How to Read This Repository + +If you are new to OTA systems, simply start with Chapter 1 and continue in order. + +If you already have embedded Linux experience, feel free to jump directly to topics that interest you. + +If you are looking for implementation details, the accompanying examples provide practical demonstrations of the concepts discussed in the documentation. + +--- + +## OTA at a Glance + +The following diagram illustrates the overall update lifecycle that will be explored throughout this repository. + +```text + OTA Server + │ + Signed Update + │ + ┌───────────▼───────────┐ + │ Download Manager │ + └───────────┬───────────┘ + │ + Verify Signature + │ + Verify Integrity + │ + Install Update + │ + Mark Boot Target + │ + Reboot Device + │ + Bootloader Decision + ┌─────────┴─────────┐ + │ │ + Boot Success Boot Failure + │ │ + ▼ ▼ + Commit Update Rollback +``` + +Each stage of this process will be examined in detail in the chapters that follow. + +--- + +## Contributing + +Contributions, suggestions, and discussions are welcome. + +If you have ideas for improvements, additional examples, or alternative approaches, feel free to open an issue or submit a pull request. + +--- + +## License + +This repository is released under the MIT License. + +See the LICENSE file for details.